for cups, goblets, and' vases, as the unusually large number of
antiques in this stone proves, yet it was not employed for
engraving until the Renaissance, when it came into use for
jewelry. Specimens of engraving on crystal, the work of this
period, are seen at Naples, Florence, and in other modern collections.
Amethyst, of the quartz species, was an attractive stone for
the engraver of nearly all nations and periods, judging from the
Egyptian, Etruscan, Greek, and Roman intagli in this variety.
A few of the most celebrated examples are : Omphale, in the
Marlborough collection ; Atalanta, in Berlin ; Achilles, in Paris,
Pan, in the Blacas ; Sapor I., in the Devonshire ; and Mithridates, in Florence. The yellow quartz did not please the
ancients as a material for the glyptic art, but the engravers
of the fifth century, however, adopted it as a favorite. One
antique specimen is found in the British Museum.
The sardonyx, usually comprising three colors, is well
adapted for carnei ; therefore, some of the largest engravings
known are cut in this gem ; the colossal specimen in the Vatican Museum surpasses all others of the kind in size.
The onyx was frequently engraved, a remarkable specimen
being afforded by the Corinthian helmet on jasper-onyx. An
imitation of this engraving constituted the chef-d'œuvre of the
notorious Poniatowsky collection.
Plasma. — There is an intaglio on this gem, in the British
Museum, of great artistic merit. This kind of engraving was
executed in the Roman period on a rare, translucent plasma
called by Pliny green jasper. There are said to be no antiques on prase, but a large part of ancient sigils are cut on
jasper.
Red jasper. — Two of the best known engravings on this
variety of quartz are the head of Minerva, at Vienna, and that
